Electric motors for vehicular applications must meet stringent performance requirements while conforming to size and weight limitations to maintain their suitability for automotive use. Often design criteria conflict when strengthening one type of performance creates a deficiency in another equally important. For example, electric motors used for drive wheels in hybrid cars must be compact and light weight, yet powerful enough to quickly accelerate a car to a speed at which the internal combustion (IC) engine can take over. In addition, they must be efficient enough to provide a convenient driving range that consumers find acceptable and that is competitive with that of purely IC vehicles. Finally, to be truly cost effective to their owners, automotive electric motors must demonstrate durability and reliability by offering suitable performance while operating amid extremes in ambient temperatures.
Electric motors used in automotive applications may be susceptible to heat build-up because of the need for a high output from a compact and light weight unit. Furthermore, the interior of heat generating components of a motor, such as the rotor, are not usually actively cooled. Instead, internally generated heat is typically conducted through several thermal barriers including air gaps before reaching cooling jackets located at the outer periphery of a motor's housing. As a result, many key components reach high temperatures during normal operation which may accelerate wear of moving parts such as shafts, bearings, and rotors.
Accordingly, it is desirable to provide a system for improving heat dissipation in electric motors that will increase their reliability and lifespan, while lowering their overall cost of operation. In addition, it is desirable to reduce the internal operating temperature of vehicular electric motors to improve their efficiency, power output, and performance. Further, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.